Method of introducing mercury into electric discharge lamps



Patented Mar. 22, 1949 siesta meshes Basil Noel Clack, Wembley Park, England, assignor to General Electric Company, a corporation oi New York No Drawing. Application May 8, 1948, Serial No. 25,998. in Great Britain July 17, 1947 My invention relates to metal vapor electric discharge devices of the kind used as lamps for illumination purposes.

When a metal, such for example as mercury, has to be introduced into the envelope off a device of the kind referred to, it is usually either distilled into the envelope after the device has been baked, or tipped in from a side tube after the device has been sealed off the exhaust pump.

Both of these methods are usually satisfactory for bench pumping but, if automatic pumping is required, neither is easy to apply. In particular, distillation is not practicable when automatic pumping is carried-out, as is usual, through a rubber connection.

It is not possible to put the mercury into the envelope before placing the envelope on the pump because normal baking temperatures (in the region of 400 C.) cause it to distill away.

It is an object of this invention to provide a method, alternative to thoseabove referred to, for introducing mercury into the envelope of-a discharge device of the kind referred to, this raise the temperature of the mercuric omde to 800-1000 C. The mercury so liberated condenses on the walls of the envelope instead oi being distilled away as would be the case if the decomposition of the mercuric oxide took place at a higher temperature. The oxygen liberated pumped ofi, any gas out and the envelope is A binder may be rendered unnecessary by anmethod being of particular value when auto- 1 matic pumping is employed. Other objectsand advantages of my invention will appear from the following description.

"According to the present invention a method of manufacturing a mercury vapor electric discharge device of the kind set forth-comprises the steps of introducing into the envelope of the device a compound of mercury, the' compound being one which does not decompose to yield the mercury at the baking temperature but which can be decomposed to yield the mercury at a higher temperature, baking and pumping the device, allowing the device to cool to a temperature atwhich the said mercury condenses, locally heating the said compound to decompou it and thus produce the said mercury. Dumping oil any undesired gaseous product of the decomposition. and-sealing ofithe envelope. Any other'gases which may be required in the envelope can. of course, be introduced before the sealing ofl.

More particularly, the process may be carried out as follows:

A small quantity. for example, a few milli- Letters Patent of the United grams, of mercuric oxide is placed either on an electrode or electrode support or on a metal disc specially'provided for the purpose within the envelope .of a discharge device. The deviceis then baked at a temperature of about 400 C. and pumped. At this temperature the mercuric oxide does not decompose. allowed to cool to a temperature at which mercury condenses and local heating of the mercuric oxide is then carried out; for example, by eddycurrent heating or positive ion bombardment to The device is then ranging the mercuric oxide in a box which is sulllciently closed to retain the oxide but allows the products of decomposition to escape. A suit 2211c box may be of nickel formed in two flanged ves, thus leaving crevices through which the products of decomposition can escape.

The invention is not limited to the use of mercuric oxide. Any other mercury compound which fulfills the requirements set forth maybe used.

What I claim as new and desire to secure by States is:

1. The method of manufacturing a mercury vapor electric discharge lamp which comprises the steps of introducing-into the envelope of the lamp a compound of mercury which does not decompose to yield the mercury at the lamp-baking temperature but which can be decomposed to yield the mercury at a higher temperature. baking and exhausting the lamp, after the lamp has. cooled to a temperature at which mercury condenses locally heating the compound to decompose it, evacuating any undesired gaseous product of the decomposition, and subsequently sealing oil the envelope. v

2..1he method of manufacturing a mercury vapor electric discharge lamp which comprises the steps of introducing a quantity of mercuric oxide into the envelope of the lamp, baking the lamp at a temperature of the order of 400 C. and exhausting it, after the lamp has cooled to a temperature at which mercury condenses locally heating the mercuric oxide to decompose it end condense it in the walls of the envelope, evacusting the ougen liberated by the decomposition, and subsequently sealing on the envelope.

' BASIL NOEL CLACK.

No references cited.

the flanges being spot-welded together, 

